Valve have now rolled out the latest stable update to the Steam Client which includes some nice fixes and improvements.
One issue I certainly noticed, since I am downloading games pretty much all the time is how often the Steam Client became unresponsive while downloading. Valve have improved this in the latest build, which is great.
Additionally, they fixed an issue where sometimes the recently played games list was truncated to 5 items, a rare crash was fixed where getting a local network address failed on a local network connection and a fix for when you're trying to buy or sell items in the overlay which might result in an empty browser window when Family View was active.
For Steam Input, they've added support for the PDP Faceoff Wired Pro Controller, the PowerA wired/wireless GameCube Style controllers and PowerA Enhanced Wireless Controller.
Also, the Steam community header is now hidden when in Big Picture chat. Full details available here.
Hopefully sometime later this year we might finally see the modern Steam client Valve have talked about (and leaked) a few times.